Sakineh Mohammadi Ashtiani: has been sentenced to 10 years in jail instead of hanging, according to officials. Photograph: AP

Iran has hanged almost 50 people during the past three weeks, according to human rights groups.

The International Campaign for Human Rights in Iran (ICHRI) said 47 prisoners, or an average of about one person every eight hours, have been put to death since the beginning of the new year. Most of the executions are believed to be related to drug-trafficking crimes, although at least two were of political activists.

The news came as it emerged today that Iranian officials had apparently suspended the sentence of hanging for Sakineh Mohammadi Ashtiani, a 43-year-old woman whose sentence of death by stoning for adultery sparked an international outcry.

Zohre Elahian, head of the parliamentary human rights committee, wrote in a letter to the Brazilian president, Dilma Rousseff: "Although the stoning sentence has not been finalised yet, the hanging sentence has been suspended due to her children's pardon." According to Elahian, Mohammadi Ashtiani has been sentenced to 10 years in jail.

In recent weeks, Iranian officials have made confusing and often contradictory comments about the fate of Mohammadi Ashtiani in hope of distracting attention from the executions or arrests of the political activists.

Drewery Dyke, of Amnesty International, said: "Issuing old news about the fate of Sakineh Mohammadi Ashtiani, by way of a letter from a parliamentarian to the president of Brazil, Dilma Rousseff, is being used to distract from the more pressing news about the rate of executions in the country."

According to the ICHRI, Iran executes more people per capita than any other country, and in absolute numbers is second only to China. Iran executed at least 179 people in 2010 and 388 in 2009.

The two known political activists hanged recently were Ali Saremi, accused of waging war on God, and Hossein Khezri, a Kurdish prisoner accused of belonging to the Pejak, an armed Kurdish opposition group.

Hadi Ghaemi, executive director of the ICHRI, said: "There are many questions about proper legal proceedings, charges against executed people, and even their identities. There are serious concerns about the abuse of the judiciary by intelligence and security forces to push their agenda through such widespread executions."

Activists believe that Iran has launched a campaign against active members of its Kurd minority. According to the ICHRI, at least 14 Kurdish activists are in danger of execution.

Today HRANA, a human rights website, reported that a 16-year-old high school student was facing imminent execution in Iran. Fatemeh Salbehi, a juvenile offender, is sentenced to death after being convicted of murder.